1. Field of the Invention
The present invention relates to a glow discharge emission spectroscopic analysis apparatus, wherein a sample is arranged so as to face an anode of a glow discharge tube, an inert gas is supplied to the sample surface under low pressure and a glow discharge is emitted by applying a high-frequency voltage or a DC voltage between the sample and the anode so that a discharge emission can be analyzed and more specifically to an improvement in mounting and applying a potential voltage to a sample, such as a large semiconductor wafer.
2. Description of Related Art
One example of a glow discharge emission spectroscopic analysis apparatus is a high-frequency glow discharge emission spectroscopic analysis apparatus which can be utilized for chemical analysis of conductor, non-conductor and a semiconductor materials. With such an apparatus, sputtering and atomic emissions are combined for analyzing bulk solids and depth profiling surfaces and coatings.
According to recent developments in semiconductor techniques, the diameter of a semiconductor wafers such as silicon wafers used in manufacturing semiconductor circuit chips have become larger and the spacing between circuit paths have decreased so that minute impurities can impair the production of such products.
Thus, the prior art is seeking to find apparatus and procedures to precisely measure the properties of large semiconductor wafers.
The present invention provides a glow discharge emission spectroscopic analysis apparatus which is capable of making a desired chemical analysis with excellent reproducibility.
In order to achieve the above object, according to the present invention, in a glow discharge emission spectroscopic analysis apparatus where a sample is arranged so as to face an anode of a glow discharge tube provided in a Faraday cage, and an inert gas is supplied to the sample surface under a low pressure, and a glow discharge is emitted by applying a high-frequency voltage or a DC voltage between the sample and anode so that the discharge emission can be analyzed, the sample is maintained at the same potential as that of a negative electrode of the high frequency voltage or DC voltage provided on one of a front surface and a back surface of the sample excluding the sputtered position.
In the glow discharge emission spectroscopic analysis apparatus having the above structure, a voltage is applied to the sample uniformly, and intensity of the discharge emission becomes stable, and thus desired and stable analyzed results can be obtained.
In one embodiment, the sample can be held by a first electrical conductor provided on one side of the glow discharge tube and second electrical conductor which is capable of being close to or separated from the first electrical conductor, and both the electrical conductors are electrically connected with each other when the sample is mounted so that a negative electric potential is provided to both of the electrical conductors.
In the glow discharge emission spectroscopic analysis apparatus having the above structure, the sample is sandwiched between the first electrical conductor and the second electrical conductors. As a result, a voltage is applied to the sample uniformly, and the intensity of the discharge emission becomes stable, and thus desired and stable analyzed results can be obtained.
Further, in the glow discharge emission spectroscopic analysis apparatus, the first electrical conductor is provided to one end of the glow discharge tube, whereas the second electrical conductor is movable by a cylinder rod so that the sample can be held between both the electrical conductors. As a result, the sample can be held simply and securely in a predetermined posture.
The present invention can be provided to measure the properties of semiconductor wafers of a large size and the first and second electrical conductors can be designed to carefully hold the semiconductor wafer without exerting undue stress, while also providing a uniform application of voltage to both sides of the semiconductor wafer. An electrical conducting wiper can be provided to interconnect the first and second electrical conductors when they are closed on the semiconductor wafer for positioning the semiconductor wafer in a sealing relationship as a cathode in the glow discharge apparatus.